- Email: [email protected]
Reactivity of (dtc)BiCl2 (dtc = diethyldithiocarbamate) towards phenyllithium: Synthesis and characterization of novel organometallic tetradentate bismuth(III) complexes
Polyhedron Vol. 12, No. 9, pp. 1079-1081, Printed in Great Britain
1993
0
0277-53X7/93 $6.00+.00 1993 Pergamon Press Ltd
REACTIVITY OF (dtc)BiCl* (dtc = DIETHYLDITHIOCARBAMATE) TOWARDS PHENYLLITHIUM : SYNTHESIS AND CHARACTERIZATION OF NOVEL ORGANOMETALLIC TETRADENTATE BISMUTH(III) COMPLEXES R. SHUKLA
and P. K. BHARADWAJ*
Department of Chemistry, Indian Institute of Technology, Kanpur 208016, India (Received 10 September 1992 ; accepted 9 December 1992) Abstract-Two tetradentate organometallic complexes of bismuth(II1) have been synthesized in high yields from the reactions of (dtc)BiCl, with phenyllithium in 1: 1 and 1: 2.5 molar ratios. These complexes were characterized by elemental analysis, IR and NMR spectroscopy. In Bi(dtc)PhCl (1) the bismuth(II1) ion is coordinated to a dtc, a chloride and a phenyl group, thus providing the first example of a bismuth(II1) complex having three different types of ligation. The other complex has ligation from two phenyl groups in addition to one dtc.
The dithiocarbamate anion (dtc) can bind strongly to transition as well as non-transition metal ions and a large number of dithiocarbamato complexes are known. ‘-3 Our interest in bismuth chemistry stems from the facts that it is a relatively unexplored area and some bismuth compounds are used as heterogeneous catalysts. 4,5 We have initiated6 a research program to explore the chemistry of bismuth in the +3 oxidation state with the ultimate goal of preparing catalytically active compounds. The difficulty in isolating pure bismuth compounds lies in the facile formation of BiO’ in the presence of moisture unless the solutions are very acidic.7 However, bismuth(II1) being a heavy metal has a very strong affinity towards sulphur donor ligands. Thus, an aqueous solution of sodium dialkyldithiocarbamate reacts readily with an alcoholic solution of BiC13to form Bi(dtc), in high yields. 3Even when BiOCl is allowed to react with an excess of dtc, the Bi(dtc)3 can be isolated in good yields,’ indicating the high stability of such bonding. In studying the reactivity of (dtc)BiC12 our assumption was that the bonding between dtc and bismuth(II1) being quite stable should remain intact during cleavage of Bi-Cl bonds by various reagents, giving rise to the formation of new compounds.8 When the (dtc)
BiC12 complex was allowed to react with phenyllithium different bismuth(II1) complexes could be isolated, depending upon the ratio of the reactants used. In the present paper we describe the facile syntheses of two such new bismuth(II1) complexes and their characterization in the solid state. EXPERIMENTAL Materials
Bismuth trichloride and tetraethylthiuram disulphide were purchased from Aldrich, while carbon disulphide, diethylamine, sodium hydroxide, phenyl bromide and the solvents were obtained from SD Fine Chemicals, India. Lithium metal in the form of wire was acquired from Fisher Scientific. All the solvents, phenyl bromide and diethylamine were purified using standard procedures9 prior to use. The reactions were carried out under dry nitrogen unless otherwise mentioned. Proton NMR spectra were recorded on a Bruker WP-80 FT instrument using TMS as the internal standard. IR spectra were recorded on an Acculab10 IR spectrophotometer. Conductivity data in acetonitrile were obtained using an all-glass model 82-CT conductivity bridge. Microanalyses were performed at the Central Drug Research Institute, * Author to whom correspondence should be addressed. Lucknow, India. 1079
R. SHUKLA
1080
and P. K. BHARADWAJ
Et
2- N -
C/S\Bi/Ph
‘5’
‘Cl
I E12-N-C/s\BiC12 ‘5’
Fig. 1. Synthetic scheme for complexes 1 and 2.
Synthesis of the complexes Syntheses of the complexes are shown schematically in Fig. 1. Bi(dtc)Cl,. This compound was prepared’ by reacting BiC13 with Bi(dtc)k in a 2 : 1 molar ratio in an acetonitrile-chloroform mixed solvent system at room temperature. The crystal structure of this compound has been determined. lo It forms an extended chloride-bridged species in the solid state. Bi(dtc)PhCl (1). This compound could be prepared by allowing phenyllithium to react with Bi(dtc)Cl, in a 1 : 1 molar ratio in THF medium at 0°C. Lithium metal (0.16 g, 0.023 mol) was added to THF (50 cm3), followed by freshly distilled bromobenzene (0.37 g, O&23 mol) dropwise with constant stirring. All the Iithium dissolved in ca 1 h. At this point solid Bi(dltc)Cl, (1.0 g, 0.023 mol) was added to the solution1 in small portions. After the addition was complete, in 0.5 h, the resulting yellow solution was kept at room temperature for another 2 h and then filtered. The filtrate evaporated to dryness and the yellow residual solid was dissolved in acetone and iallowed to evaporate at room temperature. A light yellow microcrystalline solid deposited, which was collected by filtration and air-dried. Yield 52% ; m.p. 125127°C. Bi(dtc)Ph, (2). When phenyllithium and Bi(dtc) Cl* was allowed to react in a 2.5 : 1 molar ratio under warm conditions (5@-6O’C)both the chloride groups were replaced by the phenyl groups to give the title compound in 66%1yield. Elemental analyses and ‘H NMR data for the two complexes are given in Table 1. RESULTS
ANIj DISCUSSION
Both of the complexes are stable in air in the solid state, as well as in solvents like acetone, acetonitrile, etc. Both behave as nonelectrolytes in the above
two solvents, signifying that the integrity of the complexes remains intact in these solvents. Selective IR spectral data for 1 and 2 and related complexes are collected in Table 1. Both 1 and 2, as well as other dithiocarbamato complexes of bismuth(III), show two strong peaks in the region 145G1550 cm-‘. However, triphenyl bismuthine does not absorb appreciably in this region and hence, these two peaks are associated with carbon-nitrogen stretching vibrations. Transition metal complexes of dialkyldithiocarbamato ligands are reported to show absorption in this region due to C-N stretching vibrations.3 Positions of these absorptions fall between C-N single and C=N double bonds,’ ’ signifying partial double-bond character for this bond. The 95&1050 cm-’ region is associated with v(CSS) vibrations. However, the phenyl group absorbs strongly in this region and hence, no comment can be made regarding the v(CSS) vibrations. The complexes (dtc)BiCl, and 1 show three sharp peaks in the 40&300 cm-’ region, which are not present either in the spectrum of 2 or in the spectrum of the (dtc)3Bi complex. These vibrations are assigned as the Bi-Cl stretching vibrations. Bi-Cl stretching vibrations are reported’* to occur in this region. The NMR spectral data for the complexes are also given in Table 1. For complex 1 the ratio of integration of the aliphatic and the aromatic protons is 1 : 1, indicating the formation of the complex as shown in Fig. 1. An alternative structure of 1 can be a chloride-bridged dimer or polymer. However, in the absence of an X-ray structure, it cannot be said with certainty whether the structure is monomeric or dimeric. However, the FAB-mass data showed a peak at 434, which is attributable to the cation [(Ph)Bi(dtc)]+. The NMR spectrum of complex 2 shows the ratio of integration of the aliphatic and aromatic protons as 1 : 2 and it is most likely a discrete monomeric complex, as shown in Fig. 1.
1081
Reactivity of (dtc)BiCl, towards phenyllithium Table 1. Selective IR spectral bands of 1, 2 and some related bismuth(II1) compounds 1 and 2
Compound
‘H NMR peaks IR bands (cm ‘) (80 MHz, CDCl,, SiMe,) (selective)
Analysis (%) N H
S
1.2(t, 6H, 2CH3) 3.7(q, 4H, 2CH,) 7.3(m, 5H, aromatic)
27.9(28.1)
3.3(3.2)
3.0(3.0)
13.8(13.6)
1485(sb)
1.3(t, 6H, 2CH3)
39.5(39.9)
3.7(3.9)
2.6(2.7)
12.2(12.5)
1430(sb)
3.8(q, 4H, 2CHJ 7.4(m, lOH, aromatic)
1
1480(sb) 1420(sb) 380(w) 345(m) 300(m)
2
(dtc)BiCl,
C
and analytical data” for
1515(sb) 144O(sb) 390(w) 365(s) 305(w)
(dtc),Bi
1500(sb) 1490(s) 1430(s)
“Values in parentheses are calculated.
The electronic spectra of the complexes do not show any LMCT or MLCT transitions involving bismuth(II1) and are not discussed here. Acknowledgement-We thank the Council of Scientific and Industrial Research, New Delhi, India, for financial support of this work.
REFERENCES 1. J. Willemse, J. A. Cras, J. J. Steggerda and C. P. Keijzers, Struct. Bonding (Berlin) 1976, 28, 83. 2. L. H. Pignolet, Top. Curr. Chem. 1975,56,91. 3. D. Coucouvanis, Prog. Znorg. Chem. 1970, 11, 233; D. Coucouvanis, Prog. Znorg. Chem. 1979,26,301. 4. R. K. Grasselli and J. D. Burrington, Adv. Catal. 1981,30, 133. 5. R. K. Grasselli, J. Chem. Educ. 1986,63,216.
6. B. R. Srinivasan and P. K. Bharadwaj, Znorg. Chim. Acta 1990, 178, 165 ; S. Mandal, G. Mandal, R. Shukla and P. K. Bharadwaj, Znd. J. Chem. 1992, 31A, 128. 7. C. F. Baes and R. E. Mesmer, The Hydrolysis of Cations, p. 377. John Wiley, New York (1976). 8. P. K. Bharadwaj and W. K. Musker, Znorg. Chem. 1987,26, 1453.
9. D. D. Perin, W. L. F. Armarego and D. R. Perrin, PuriJication of Laboratory Chemicals. Pergamon Press, Oxford (1980). 10. B. R. Srinivasan, P. K. Bharadwaj and A. H. White, unpublished results. 11. K. Nakamoto, Infrared and Raman Spectra of Znorganic and Coordination Compounds, 4th edn, p. 346. John Wiley, New York (1986) and refs cited therein. 12. J. D. Smith, in Comprehensive Inorganic Chemistry (Edited by A. F. Trotman-Dickerson), Vol. 2, pp. 591-592. Pergamon Press, Oxford (1973).
1993
0
0277-53X7/93 $6.00+.00 1993 Pergamon Press Ltd
REACTIVITY OF (dtc)BiCl* (dtc = DIETHYLDITHIOCARBAMATE) TOWARDS PHENYLLITHIUM : SYNTHESIS AND CHARACTERIZATION OF NOVEL ORGANOMETALLIC TETRADENTATE BISMUTH(III) COMPLEXES R. SHUKLA
and P. K. BHARADWAJ*
Department of Chemistry, Indian Institute of Technology, Kanpur 208016, India (Received 10 September 1992 ; accepted 9 December 1992) Abstract-Two tetradentate organometallic complexes of bismuth(II1) have been synthesized in high yields from the reactions of (dtc)BiCl, with phenyllithium in 1: 1 and 1: 2.5 molar ratios. These complexes were characterized by elemental analysis, IR and NMR spectroscopy. In Bi(dtc)PhCl (1) the bismuth(II1) ion is coordinated to a dtc, a chloride and a phenyl group, thus providing the first example of a bismuth(II1) complex having three different types of ligation. The other complex has ligation from two phenyl groups in addition to one dtc.
The dithiocarbamate anion (dtc) can bind strongly to transition as well as non-transition metal ions and a large number of dithiocarbamato complexes are known. ‘-3 Our interest in bismuth chemistry stems from the facts that it is a relatively unexplored area and some bismuth compounds are used as heterogeneous catalysts. 4,5 We have initiated6 a research program to explore the chemistry of bismuth in the +3 oxidation state with the ultimate goal of preparing catalytically active compounds. The difficulty in isolating pure bismuth compounds lies in the facile formation of BiO’ in the presence of moisture unless the solutions are very acidic.7 However, bismuth(II1) being a heavy metal has a very strong affinity towards sulphur donor ligands. Thus, an aqueous solution of sodium dialkyldithiocarbamate reacts readily with an alcoholic solution of BiC13to form Bi(dtc), in high yields. 3Even when BiOCl is allowed to react with an excess of dtc, the Bi(dtc)3 can be isolated in good yields,’ indicating the high stability of such bonding. In studying the reactivity of (dtc)BiC12 our assumption was that the bonding between dtc and bismuth(II1) being quite stable should remain intact during cleavage of Bi-Cl bonds by various reagents, giving rise to the formation of new compounds.8 When the (dtc)
BiC12 complex was allowed to react with phenyllithium different bismuth(II1) complexes could be isolated, depending upon the ratio of the reactants used. In the present paper we describe the facile syntheses of two such new bismuth(II1) complexes and their characterization in the solid state. EXPERIMENTAL Materials
Bismuth trichloride and tetraethylthiuram disulphide were purchased from Aldrich, while carbon disulphide, diethylamine, sodium hydroxide, phenyl bromide and the solvents were obtained from SD Fine Chemicals, India. Lithium metal in the form of wire was acquired from Fisher Scientific. All the solvents, phenyl bromide and diethylamine were purified using standard procedures9 prior to use. The reactions were carried out under dry nitrogen unless otherwise mentioned. Proton NMR spectra were recorded on a Bruker WP-80 FT instrument using TMS as the internal standard. IR spectra were recorded on an Acculab10 IR spectrophotometer. Conductivity data in acetonitrile were obtained using an all-glass model 82-CT conductivity bridge. Microanalyses were performed at the Central Drug Research Institute, * Author to whom correspondence should be addressed. Lucknow, India. 1079
R. SHUKLA
1080
and P. K. BHARADWAJ
Et
2- N -
C/S\Bi/Ph
‘5’
‘Cl
I E12-N-C/s\BiC12 ‘5’
Fig. 1. Synthetic scheme for complexes 1 and 2.
Synthesis of the complexes Syntheses of the complexes are shown schematically in Fig. 1. Bi(dtc)Cl,. This compound was prepared’ by reacting BiC13 with Bi(dtc)k in a 2 : 1 molar ratio in an acetonitrile-chloroform mixed solvent system at room temperature. The crystal structure of this compound has been determined. lo It forms an extended chloride-bridged species in the solid state. Bi(dtc)PhCl (1). This compound could be prepared by allowing phenyllithium to react with Bi(dtc)Cl, in a 1 : 1 molar ratio in THF medium at 0°C. Lithium metal (0.16 g, 0.023 mol) was added to THF (50 cm3), followed by freshly distilled bromobenzene (0.37 g, O&23 mol) dropwise with constant stirring. All the Iithium dissolved in ca 1 h. At this point solid Bi(dltc)Cl, (1.0 g, 0.023 mol) was added to the solution1 in small portions. After the addition was complete, in 0.5 h, the resulting yellow solution was kept at room temperature for another 2 h and then filtered. The filtrate evaporated to dryness and the yellow residual solid was dissolved in acetone and iallowed to evaporate at room temperature. A light yellow microcrystalline solid deposited, which was collected by filtration and air-dried. Yield 52% ; m.p. 125127°C. Bi(dtc)Ph, (2). When phenyllithium and Bi(dtc) Cl* was allowed to react in a 2.5 : 1 molar ratio under warm conditions (5@-6O’C)both the chloride groups were replaced by the phenyl groups to give the title compound in 66%1yield. Elemental analyses and ‘H NMR data for the two complexes are given in Table 1. RESULTS
ANIj DISCUSSION
Both of the complexes are stable in air in the solid state, as well as in solvents like acetone, acetonitrile, etc. Both behave as nonelectrolytes in the above
two solvents, signifying that the integrity of the complexes remains intact in these solvents. Selective IR spectral data for 1 and 2 and related complexes are collected in Table 1. Both 1 and 2, as well as other dithiocarbamato complexes of bismuth(III), show two strong peaks in the region 145G1550 cm-‘. However, triphenyl bismuthine does not absorb appreciably in this region and hence, these two peaks are associated with carbon-nitrogen stretching vibrations. Transition metal complexes of dialkyldithiocarbamato ligands are reported to show absorption in this region due to C-N stretching vibrations.3 Positions of these absorptions fall between C-N single and C=N double bonds,’ ’ signifying partial double-bond character for this bond. The 95&1050 cm-’ region is associated with v(CSS) vibrations. However, the phenyl group absorbs strongly in this region and hence, no comment can be made regarding the v(CSS) vibrations. The complexes (dtc)BiCl, and 1 show three sharp peaks in the 40&300 cm-’ region, which are not present either in the spectrum of 2 or in the spectrum of the (dtc)3Bi complex. These vibrations are assigned as the Bi-Cl stretching vibrations. Bi-Cl stretching vibrations are reported’* to occur in this region. The NMR spectral data for the complexes are also given in Table 1. For complex 1 the ratio of integration of the aliphatic and the aromatic protons is 1 : 1, indicating the formation of the complex as shown in Fig. 1. An alternative structure of 1 can be a chloride-bridged dimer or polymer. However, in the absence of an X-ray structure, it cannot be said with certainty whether the structure is monomeric or dimeric. However, the FAB-mass data showed a peak at 434, which is attributable to the cation [(Ph)Bi(dtc)]+. The NMR spectrum of complex 2 shows the ratio of integration of the aliphatic and aromatic protons as 1 : 2 and it is most likely a discrete monomeric complex, as shown in Fig. 1.
1081
Reactivity of (dtc)BiCl, towards phenyllithium Table 1. Selective IR spectral bands of 1, 2 and some related bismuth(II1) compounds 1 and 2
Compound
‘H NMR peaks IR bands (cm ‘) (80 MHz, CDCl,, SiMe,) (selective)
Analysis (%) N H
S
1.2(t, 6H, 2CH3) 3.7(q, 4H, 2CH,) 7.3(m, 5H, aromatic)
27.9(28.1)
3.3(3.2)
3.0(3.0)
13.8(13.6)
1485(sb)
1.3(t, 6H, 2CH3)
39.5(39.9)
3.7(3.9)
2.6(2.7)
12.2(12.5)
1430(sb)
3.8(q, 4H, 2CHJ 7.4(m, lOH, aromatic)
1
1480(sb) 1420(sb) 380(w) 345(m) 300(m)
2
(dtc)BiCl,
C
and analytical data” for
1515(sb) 144O(sb) 390(w) 365(s) 305(w)
(dtc),Bi
1500(sb) 1490(s) 1430(s)
“Values in parentheses are calculated.
The electronic spectra of the complexes do not show any LMCT or MLCT transitions involving bismuth(II1) and are not discussed here. Acknowledgement-We thank the Council of Scientific and Industrial Research, New Delhi, India, for financial support of this work.
REFERENCES 1. J. Willemse, J. A. Cras, J. J. Steggerda and C. P. Keijzers, Struct. Bonding (Berlin) 1976, 28, 83. 2. L. H. Pignolet, Top. Curr. Chem. 1975,56,91. 3. D. Coucouvanis, Prog. Znorg. Chem. 1970, 11, 233; D. Coucouvanis, Prog. Znorg. Chem. 1979,26,301. 4. R. K. Grasselli and J. D. Burrington, Adv. Catal. 1981,30, 133. 5. R. K. Grasselli, J. Chem. Educ. 1986,63,216.
6. B. R. Srinivasan and P. K. Bharadwaj, Znorg. Chim. Acta 1990, 178, 165 ; S. Mandal, G. Mandal, R. Shukla and P. K. Bharadwaj, Znd. J. Chem. 1992, 31A, 128. 7. C. F. Baes and R. E. Mesmer, The Hydrolysis of Cations, p. 377. John Wiley, New York (1976). 8. P. K. Bharadwaj and W. K. Musker, Znorg. Chem. 1987,26, 1453.
9. D. D. Perin, W. L. F. Armarego and D. R. Perrin, PuriJication of Laboratory Chemicals. Pergamon Press, Oxford (1980). 10. B. R. Srinivasan, P. K. Bharadwaj and A. H. White, unpublished results. 11. K. Nakamoto, Infrared and Raman Spectra of Znorganic and Coordination Compounds, 4th edn, p. 346. John Wiley, New York (1986) and refs cited therein. 12. J. D. Smith, in Comprehensive Inorganic Chemistry (Edited by A. F. Trotman-Dickerson), Vol. 2, pp. 591-592. Pergamon Press, Oxford (1973).